Investigation of the effects of vitamin D and calcium on intestinal motility: In vitro tests and implications for clinical treatment

The presence of vitamin D receptors in small intestine muscle cells may lead one to think that vitamin D may act locally, influencing intracellular calcium concentration and contributing to the contraction-relaxation regulation of the intestinal smooth muscle cells. This study investigates the potential effects of vitamin D and calcium on intestinal motility using an in vitro test.

Different calcium concentrations added to the tissue not pre-treated with 1,25-dihydroxycholecalciferol [1α,25(OH)₂D₃] produced no response at low doses (1.25 × 10⁻³ and 2.0 × 10⁻³ mol L⁻¹) and only a very weak response at higher concentration (3.0 × 10⁻³ mol L⁻¹). The addition of 1α,25(OH)₂D₃ (1.44 × 10⁻¹⁰ mol L⁻¹) had no effect on isolated ileum motility. When calcium (3.0 × 10⁻³ mol L⁻¹) was added after at least 3 hours, it evoked evident and persistent contractions for 60–90 minutes. The contractions were at about 40 % of the peak produced by acetylcholine. Thus, simultaneous intake of vitamin D and calcium might be a useful co-adjuvant in intestinal atony therapy aimed to stimulate normal gut motility in humans. These findings imply that supplemental vitamin D may be important in all cases where calcium has to be prescribed.